Finding the Third Proportional to 58.78 and 90.42

Step by Step Solution

1. Step 1: Write the proportion equation
   58.78 : 90.42 = 90.42 : x
2. Step 2: Convert to fraction form
   58.78/90.42 = 90.42/x
3. Step 3: Cross multiply
   58.78x = 90.42 × 90.42
4. Step 4: Simplify right side
   58.78x = 8,176.12
5. Step 5: Solve for x
   x = 8,176.12/58.78
6. Step 6: Final answer
   x = 139.09